WHEN oil companies want to squeeze more crude out of an oil well, they usually turn to experts in physics, chemistry or engineering. But they are looking in the wrong place. The answer lies in biology.
That at least is the view of microbiologist Bill Costerton, who told a meeting of the Australian Society for Microbiology in Melbourne last week that the tough colonies of living bacteria known as biofilms could make oil wells up to 20 per cent more productive.
Typically, only one-third of the oil in an oilfield can be brought to the surface. Some is forced out by gas pressure when a well is drilled, and engineers can sometimes pump water in to drive out more. But if the water escapes through layers of permeable rock called stringers, this strategy will fail. And although plastics can be used to block stringers or even to increase the viscosity of the water, they are very expensive.
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Now Costerton, who studies biofilms at Montana State University in Bozeman, and his colleague Al Cunningham, have developed a new way of blocking stringers. They have found a way to encourage tiny bacteria to club together to form a biofilm plug that blocks the fissures.
A biofilm forms when bacteria congregate to form a colony that encases itself in a matrix of slime made of sugary polymers called polysaccharides. Biofilms grow on every surface where there are bacteria 鈥� from your teeth, where they can create plaque, to the inside of sewage pipes.
To make their biofilm plugs, the Montana team first starve bacteria, stimulating them to form minuscule dormant ultramicrobacteria, or UMBs. These are a fraction of the size of well-fed bacteria, and when pumped into a well they can penetrate pores as small as 2 micrometres wide.
Once the UMBs are in position, a liquid nutrient such as molasses is pumped in to stimulate them to grow back to their usual size and to multiply. As they multiply, they produce four times their own volume in slime, forming the biofilms that plug the stringers.
To know when to pump in the molasses, the technicians need to work out when the UMBs have infiltrated the stringers. One way they do this is by engineering the bacteria to make them resistant to an antibiotic. The number of antibiotic-resistant bugs in the water flowing out of the well gives an indication of how well the bugs have infiltrated the field in that area. In some cases, it is possible to track the bacteria by their appearance alone, say Costerton.
In their first attempt to use the UMB technique, they successfully blocked one stringer in an oil well in Saskatchewan, Canada. Unfortunately the well had other stringer that prevented the engineers extracting any more oil, but they are now gearing up for a second attempt on the Bell Creek oilfield in Montana. The technology has been licensed to MSE-Technologies, a mining company in Butte, Montana.
But Hermanta Sarma of the Santos School of Petroleum Engineering at the University of Adelaide warns that the biohazard risks in using microbes to recover oil still need to be addressed. Last year, while working for a Japanese oil company, he tested another microbial technique for recovering oil from wells in China. He also warns that the bugs can block pipelines.
But Costerton is confident his biofilm technique will work. 鈥淲e imagine being able to plug a crab鈥檚 ass at four fathoms. That鈥檚 tight,鈥� he jokes.